The present invention relates to a ceiling board, a designing method for the ceiling board, a manufacturing method for the ceiling board, a magnet cover, a magnet system and a magnetic resonance imaging apparatus, and more particularly to a horizontally supported ceiling board, a designing method for such a ceiling board, a manufacturing method for such a ceiling board, a magnet cover having such a ceiling board, and a magnet system having such a cover, and a magnetic resonance imaging apparatus provided with such a magnet system.
In a magnetic resonance imaging (MRI) apparatus, the subject of imaging is brought into the internal space of its magnet system, i.e. an imaging space in which a magnetostatic field is formed, a gradient magnetic field and a high frequency magnetic field are applied to the subject, magnetic resonance signals are generated from spins therein, and an image is reconstructed on the basis of the signals so received.
A magnet system of a vertical magnetic field type has a magnet body having an upper pole section and a lower pole section opposite to each other in the vertical direction with the imaging space between them. The magnet body is housed in a magnet cover. The magnet cover has a ceiling board covering the end face of the upper pole section and a floor board covering the end face of the lower pole section, and the space between these ceiling board and floor board serves as the imaging space. In a full human body size magnetic resonance imaging apparatus, the diameter of the upper pole section and the lower pole section is almost 1 m, and the ceiling board and the floor board have correspondingly large diameters.
In order to efficiently form a required magnetic field space, as a magnet system has its upper pole section and lower pole section to be opposite to each other at the minimum required distance between them, the distance between the ceiling board and the floor board tends to be short. Therefore, when the ceiling board is bent by its own weight, its distance from the floor board is correspondingly shortened, making it more difficult for a patient with a head coil on, for instance, to be brought into the imaging space.